In the recent decade, more and more data needs to be transmitted as the rapid development of the wireless local area network and mobile communications. It is an important and urgent task to satisfy the growing number of users and a higher transmission rate and to guarantee a higher communication quality with limited spectrum resources. In the late 90s of the last century, Bell Laboratory took the lead in applying the concept of a MIMO (Multiple Input Multiple Output) system in a mobile communication system, and proved theoretically and experimentally that MIMO was able to greatly increase the capacity and quality of the mobile communication system, which drew great attention from scholars. The MIMO technology developed rapidly in a short few years, and has become the core technology of a new generation of mobile communication systems (3G, LTE) and a new generation of wireless local area networks 802.11n (Wi-Fi) and 802.16 wireless metropolitan area networks WiMax.
Multiple antennas are placed at both the transmitting end and the receiving end of a MIMO system, and a diversity technique and a multiplexing technique are rationally used so that the capacity of the wireless communication system is increased and the bit error rate of the system is reduced simultaneously. Especially in an environment having rich multipath components, the MIMO system shows huge potential in increasing the capacity of the system. The MIMO system also uses a beamforming (Beamforming) technique to focus energy in a specific direction (or some specific directions) so that the main lobe points to the signal direction, and meanwhile nulling is performed on interference signals, thereby realizing a wider coverage and having inhibitory effects on the interference signals.
In the MIMO system, multiple antennas are used at both the receiving end and the transmitting end, so the design of the antennas in the MIMO system is a key point and a difficult point in the overall system design. In order to construct a MIMO system with high efficiency, the design style of an antenna array is usually adopted at the transmitting end of the system, and meanwhile the beamforming technique is adopted, so as to form an intelligent antenna array suitable for the MIMO system. Compared with a conventional omnidirectional antenna array, such intelligent antenna array enables the MIMO system to obtain a higher capacity, a lower bit error rate, a wider coverage and stronger interference inhibition performance.
An existing intelligent antenna apparatus includes an intelligent antenna array and a beam switching network. The antenna array and the beam switching network are usually printed on one dielectric substrate, so as to facilitate installation and reduce costs. The main factors that are considered in the existing intelligent antenna design are how to make the intelligent antenna array cover the entire space, and how to enhance signals in the direction of users and to inhibit interference signals simultaneously. In order to inhibit the interference signals, a directional pattern of the antenna is usually made into a unilateral beam, and in order to obtain an antenna directional pattern having orientation characteristics, a reflector is added to the antenna. However, a certain distance shall be kept between the beam switching network and the antenna, so that the addition of the reflector further increases the size of the system. The size of the antenna apparatus and the performance of the antenna apparatus contradict each other, and it is difficult to improve the performance of the antenna apparatus without increasing the size of the antenna apparatus.